SETI is a novel new search strategy for alien life close to home

It’s one of the biggest questions in modern science. If intelligent life is common in the universe, then where are they?

First proposed by Physicist Enrico Fermi over lunch in 1950, this simple question has become a central tenet of the Search for Extraterrestrial Intelligence (SETI) over the past few decades.

Since Fermi first raised the question, there have been many proposed solutions that are as bad as science fiction movies addressing the issue. Of course, the simplest and most nagging solution is that we’re it, or that intelligent species are so widely separated in space and time, that we’re effectively alone. Of course, UFO abductees take the opposite track, insisting that we’re visited by an alien civilization every long weekend, a claim with a conspicuous lack of evidence.

Since the original Project Ozma was conducted by Frank Drake in 1960, SETI has scoured the sky in search of alien signals. But a recent paper by Michaël Gillon of the Astrophysics Institute in Liège, Belgium suggests an interesting new search strategy much closer to home.

A proposed method of efficent interstellar transmission. Created by Author

It’s worth considering just how E.T. might explore the galaxy, and what kinds of relics a civilization millions of years old would leave behind. For example, over the last 50+ years that humanity has been a space-faring civilization, we’ve launched five spacecraft destined to escape our solar system: Voyagers 1 and 2, Pioneers 10 and 11, and New Horizons, which will conduct a flyby of Pluto in July 2015.

Gillon notes that we’ve barely begun exploring the 5×1014 cubic A.U. (1 cubic astronomical unit is a cube almost 155 million kilometres on one side) volume of the solar system from the Sun out to the Oort cloud.

If a civilization has ever explored our solar system, they may have done it in the distant past as part of a survey. Gillion proposes that the most efficient way for a civilization to correspond over vast interstellar distances might be to construct a network of Interstellar Communications Devices, or ICDs.

An message deliberately transmitted by the Arecibo Observatory at the globular cluster M13 in 1974. Arne Nordmann under a Wikimedia Commons Attribution 3.0 license

Park a receiver or transmitter out about 550 A.U.s from the Sun, and something interesting happens. Such a relay station could utilize the mass of the Sun to take advantage of an effect known as gravitational lensing to act as an amplifier to focus a signal, and vastly cut down on the energy needed to send and receive messages. One could imagine a vast web of such transmitters, strung out though the galaxy.

Of course, there’s no direct evidence that such a “galactic inter-web” exists, though it might be worth searching for. Gillion proposes that such alien relay stations, if they exist, would be parked in the directions opposite in our sky from nearby stars such as Alpha Centauri, 4.37 light years distant. The paper even calculates the rough size of such a station assuming solar sail technology is used, at just over a kilometre across. The alien transmitter/receiver would also have to periodically maneuver to follow the proper motion of the target star over millennia.

But at such vast distances, the object would shine only at +30th magnitude, right on the grim edge of what the Hubble Space Telescope can currently resolve. Occultations of distant stars as the alien artifact passed across our line of sight would be rare as well.

We may, however, be able to eavesdrop on such a hypothetical network. Gillon proposes a campaign to monitor these focal points using the recently constructed Allen Telescope Array.

Another active method would be to deliberately signal these regions, though some debate whether it would be prudent to announce our presence. One would think that there would be transmitters at other nearby stars pointed back at our solar system as well for us to possibly detect.. Keep in mind, we’ve not only been surreptitiously broadcasting our presence to the void via radio for almost a century now, but our spectral signature has also been publicizing the presence of life on Earth for hundreds of millions of years.

And we’re just approaching the ability to conduct such searches ourselves. Over 1,000 exoplanets are now known of, and future surveys will give us the capability to hunt for chemical traces of life in these respective planet’s spectra. Kepler still has thousands of exoplanets in its survey awaiting confirmation, and the TESS observatory will conduct an all sky survey starting in 2017.

An artist’s concept of TESS. Credit-MIT Kavli Institute for Astrophysics & Space Research

More exotic SETI search ideas exist, such as looking for transiting artificial geometrical shapes (think Larry Niven’s Ringworld) or hunting for waste heat from stars encircled by massive Dyson spheres. Proposed missions, such as FOCAL may one day field a distant gravitational lensing station of our own.

While the detection of an alien transmitter 500 A.U.s distant would be thrilling, think of how tantalizing it would be. Perhaps we could eavesdrop, but we’d also want to take a look. Our most distant spacecraft is Voyager 1 at over 125 A.U.s distant… And it took us over 36 years to get there!

Science journalist, astronomy specialist, educator. Retired from the USAF in 2007 and am now a science teacher and freelance science writer. Am out stargazing on every clear night and hope to add science... read more fiction writer to my resume!View author's profile